Choke control for carburetor



April 26, 1966 T. M. BALL CHOKE CONTROL FOR CARBURETOR Original Filed Dec. 21, 1961 INVENTOR- 7%0 7774s /%,Bd//

United States Patent 3,248,095 CHOKE CONTROL FOR CARBURETOR Thomas M. Ball, Bloomfield Hills, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Original application Dec. 21, 1961, Ser. No. 161,189. Divided and this application Oct. 7, 1963, Ser. No.

3 Claims. Cl. 261-39) This application is a division of co-pending application, Serial No. 161,189, filed December 21, 1961.

This invention relates to improvements in the automatic control of a carburetor for an internal combustion engine and has for an important object the provision of improved control means for the conventional unbalanced choke blade effective to prevent stalling of the engine immediately after it has been started.

Occasionally when an automotive engine is initially started, a rush of inlet air blows the choke blade open sufficiently'to cause the engine to stall, particularly during unfavorable weather conditions. It is accordingly another object of the invention to provide improved simple and economical means which is highly effective to enable limited opening of the choke during starting only, so as to prevent stalling, and which allows normal choke operation after the engine has been started and the throttle has once been opened beyond the idle operating condition.

It is considered desirable to provide an automatic carburetor which will enable rapid engine starting merely by closing the starting motor circuit and without supplemental manual operation of the throttle. Such operation is often referred to as cam starting because the usual fast idle cam and cooperating thermostatic control are employed to maintain the throttle in the proper starting position. During cam starting the throttle will be at an idle position, such that the engine is especially susceptible to stalling in consequence of a surge of cold inlet air immediately after being started. Another object is therefore to provide improved automatic controlmeans of the above character which is particularly adapted for cam starting, so as to limit the initial choke opening during starting only, without interfering with normal choke operation at other times.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference being had to the ac companying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a fragmentary and generally schematic view of a carburetor embodying the present invention, portions being broken away to illustrate details of construction, the choke blade being shown in the starting position.

FIGURE 2 is a view similar to FIGURE 1, showing the choke blade in an idle operating position.

It is to be understood that the'inven-tion is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

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Referring to the drawings, an embodiment of the pres- .ent invention is illustrated by way of example comprising 14 secured to a rotatable shaft 15 journalled at opposite ends in the body is provided at a downstream location of the conduit 11.

Suitably located within a portion of the engine so as to beresponsive to an operating temperature thereof is a spiral di-metallic thermostat spring 16 having a fixed end secured to a fixed spindle 18. A swinging arm 19 pivotal on spindle 18 has an outer swinging end pivotally connected. to the lower end of an operating link 21. A free end 22 of thermostat 16 is engaged with arm 19 so as to urge arm 19 counterclockwise with progressively increasing force as the temperature descreases. The upper end of link 21 is pivotally connected at 23't0 the swinging end of a crank arm 24 keyed to the choke shaft 13.

Keyed to the throttle shaft is a throttle control lever 25 having one swinging end pivotally connected at 26 with a personally actuated throttle link 27. 'The other end of lever 25 is provided with a threaded boss 28 having an adjustable idle control screw or cam follower 29 screwed therein. The inner end of screw 29 is adapted to engage a stepped cam surface 30 of a fast idle cam 31 when the latter is in a predetermined cold idle operating position as described below. The cam 31 is keyed to a rotatable axial stub 32 journalled on the body 10 and is provided with a counterweight portion 33 effective to urge clockwise rotation of cam 31 by gravity force toward a warm operating position.

Throttle lever 25 is normally urged clockwise toward the closed oridle position illustrated in FIGURES; l and 2 by a customary throttle return spring 27a schematically illustrated under tension between a projection 25a of lever 25 and a fixed portion 27b of the engine. Foot pedal actuation of shaft 27 is effective to swing lever 25 counterclockwise to open the throttle 14.

Upon closing movement of choke valve 12, the fast idle cam 31 is swung counterclockwise to the cold position by means of a link 34 having an upper end pivotally connected at 35 to a crank arm 36 keyed to shaft 13. The lower end of link 34 terminates in an extension 37 which projects in a direction parallel to the pivot axis of cam 31 through a lost motion slot 38 to complete a lost motion pivotal connection between link 34 and cam 31. Slot 38 is formed arcuately within the counterweight portion 33 concentrically with the, pivot axis of cam 31 to enable opening movement of choke valve 12 independently of movement of cam 31, as described below, by virtue of extension 37 riding within groove 38,

In order to render the position of choke valve 12 responsive to the pressure in conduit 11 downstream of throttle valve 14, a vacuum cylinder 40 formed integrally with body 10 contains a reciprocable piston 41 therein, pivotally connected at 42 to one end of a'dog-leg link 43. The other end of the latter link is pivotally connected at 44 to the outer end of a projection 45 secured to valve 12 so as to swing the latter in a clockwise opening movement upon rightward movement of piston 41. The right end shaft 13. A vertically shiftable cam rod 51 slidable in guide bushings 52 terminates in an upper pointed end 50. A rounded cam 53 is keyed to throttle shaft 15.

During operation of the structure described, when screw 29 is in contact with the steppexl cam surface 30, the frictional contact between screw 29 and surface 30 resulting from the tension of spring 27a is sufficient to prevent pivotal movement of cam 31 in consequence of i the normal forces acting thereon, such as the forces resulting from counterweight 33, thermostat coil 16, piston 41, or the downwardly flowing air in conduit 11 acting on the unbalanced blade 12. In consequence, when the carburetor parts are in the cold position illustrated in FIGURE 1 and the cold engine is initially started, opening of the unbalanced choke blade 12 by the initial surge of cold inlet air in conduit 11 will be limited to a predetermined extent, as for example approximately 10, by contact between cam arm 49 and the pointed end 50 of rod 51. Thereafter, upon opening of throttle 14 to accelerate the engine, rod 50 will move downward by gravity to enable clockwise opening of choke 12 by the force of the air flow in conduit 11 until cam arm 49 is swung beyond the point of engagement with end 50. Thereafter choke valve 12 will be free to operate in the conventional manner. In the usual instance, piston 41 will be effective to maintain arm 49 clockwise beyond end 50 during cold idling.

In the event the engine is turned off and allowed to cool, projection 49 will engage the lefthand side of point 50 as in FIGURE 2. Accordingly, in order to return the throttle to the cold starting position of FIGURE 1, it is necessary first to depress rod 51 by opening throttle 14. Thermostat spring 16 will then return choke 12 to the cold position, whereupon throttle 14 may then be returned to the closed starting position of FIGURE 4.

During the starting operation, the throttle 14 will be maintained in a fast idle position by reason of screw 29 engaging the fast idle step of the cam surface 30, FIG- URE 1. At the fast idle position, throttle 14 is cracked slightly open as illustrated in FIGURE 1, so that the engine will idle effectively in the cold condition. Thereafter, when throttle valve 14 is opened from the fast idle position to accelerate the engine, the frictional engagement between' screw 29 and cam surface 30 will be released to enable opening of choke valve 12 to the usual operating condition. By this time rod end 50 will be below the arc scribed by cam 49 and the danger of engine stalling will have passed, because the stalling tendency described occurs only in the first two or three seconds of engine operation;

After the throttle 14 has been initially opened from the starting position of FIGURE 1 to enable opening of choke valve 12 to a running position, if the throttle 14 is then returned to a cold idle position so as to engage one of the lesser steps of cam surface 30, the cam 31 will be locked against swinging movement as aforesaid by virtue'of its frictional contact with screw 29. However, the extension 37 will ride downwardly within slot 38. Thus if the engine is allowed to run at idle for sufficient time to relax the closing force of thermostat spring 16 as a result of warming of the engine, throttle valve 12 will be free to open by virtue of movement of extension 37 along slot 38.

If the engine is operated in the warm condition under load and is then turned off and allowed to cool, choke valve 12 will be locked against return movement to the closed position by contact between fast idle cam 31 and screw 29. Accordingly, in order to return the carburetor mechanism to the position illustrated in FIGURE 1,

throttle 14 must first be opened to release the engage:

ment between cam 31 and screw 29 thereby to enable thermostat spring 16 to return choke valve 12 and cam 31 to the position of FIGURE 1. Thereafter upon closing of throttle 14, screw 29 will engage the cold starting step of cam surface 30 as illustrated in FIGURE 1.

I claim:

1. In a fuel charging device for an internal combustion engine, air inlet conduit means, choke valve means in said conduit means comprising an unbalanced pivotal blade adapted to be pivoted to an open position by. the air flow in said conduit means impinging on said blade, choke valve movement limiting means cooperable with said choke valve means to move conjointly therewith in a predetermined path upon opening of said choke blade, ther-.

mostatic means responsive to decreasing temperature for yieldingly closing said choke valve, a throttle valve in said conduit means movable between open and idle posir tions, means to enable limited air flow induced opening of said choke blade to a starting position and to block further opening thereof to prevent a sudden fiow of inlet air in said conduit means sufiicient to stall said engine immediately after the latter has begun to operate under its own power with said throttle valve at its closed position comprising throttle actuated movement limiting.

means cooperable with said throttle valve to move there:

with into said path to abut said choke valve movement 1 limiting means and block air flow induced opening of said choke valve beyond said starting position upon move.

ment of said throttle valve to said idle position and to move out of said path to enable opening of said choke valve upon movement of said throttle valve from its idle 1 to its open position.

2. In a fuel charging device for an internal combustion engine, air inlet conduit means, choke valve means 1 in said conduit means comprising an unbalanced pivotal blade adapted to be pivoted to an open position by the air flow in said conduit means impinging on said blade,

thermostatic means responsive to decreasing temperature for yieldingly closing said choke valve, a throttle valve in said conduit means movable between open and idle positions, means to enable limited air flow induced open- 1 ing of said choke blade to a starting position and to block further opening thereof to prevent a sudden flow of inlet air in said conduit means suflicient to stall said engines immediately after the latter has begun to operate under its own power with said throttle valve at its closed position comprising a choke actuated projection connected with said choke valve means for swinging in a predetermined path in unison with pivoting of said blade, movement limiting means shiftable into said path to engage and block swinging of said projection upon pivotal opening of said blade to said starting position and shiftable out of said path to free said projection and blade for pivoting to said open position, and means cooperable with said throttle valve and engageable with said move- 1 ment limiting means to shift the latter into and out of said path upon movement of said throttle valve to its idle and open positions respectively.

3. In a fuel charging device for an internal combustion engine, air inlet conduit means, choke valve means in said conduit means comprising anunbalanced pivotal blade adapted to be pivoted to an open position by the air flow in said conduit means impinging on said blade, thermostatic means responsive to decreasing temperature 1 for yieldingly closing said choke valve, 21- throttle valve in said conduit means movable between open and idle positions, means to enable limited air flow induced opening of said choke blade to a starting position and to block further opening thereof to prevent a sudden flow of inlet.

air in said conduit means sufiicient to stall said engine immediately after the latter has begun to operate under its own power with said throttle valve at its closed position comprising projecting means connected with said choke blade to pivot therewith, movement limiting means.

shiftable into the path of pivotal movement of said projecting means to engage and block said movement upon pivotal opening of said blade to said starting position, means yieldingly urging shifting of said movement limiting means out of said path to free said projecting means and blade for pivoting to said open position, cam means connected with said throttle valve to move therewith and engage said movement limiting means to shift the same into said path upon movement of said throttle valve to its idle position and to release said movement limiting means for movement out of said path upon opening of said throttle valve from its idle position.

References Cited by the Examiner UNITED STATES PATENTS HARRY B. THORNTON, Primary Examiner.

0 RONALD R. WEAVER, Examiner. 

1. IN A FUEL CHARGING DEVICE FOR AN INTERNAL COMBUSTION ENGINE, AIR INLET CONDUIT MEANS, CHOKE VALVE MEANS IN SAID CONDUIT MEANS COMPRISING AN UNBALANCED PIVOTAL BLADE ADAPTED TO BE PIVOTED TO AN OPEN POSITION BY THE AIR FLOW IN SAID CONDUIT MEANS IMPINGING ON SAID BLADE, CHOKE VALVE MOVEMENT LIMITING MEANS COOPERABLE WITH SAID CHOKE VALVE MEANS TO MOVE CONJOINTLY THEREWITH IN A PREDETERMINED PATH UPON OPENING OF SAID CHOKE BLADE, THERMOSTATIC MEANS RESPONSIVE TO DECREASING TEMPERATURE FOR YIELDINGLY CLOSING SAID CHOKE VALVE, A THROTTLE VALVE IN SAID CONDUIT MEANS MOVABLE BETWEEN OPEN AND IDLE POSITIONS, MEANS TO ENABLE LIMITED AIR FLOW INDUCED OPENING OF SAID CHOKE BLADE TO A STARTING POSITION AND TO BLOCK FURTHER OPENING THEREOF TO PREVENT A SUDDEN FLOW OF INLET AIR IN SAID CONDUIT MEANS SUFFICIENT TO STALL SAID ENGINE IMMEDIATELY AFTER THE LATTER HAS BEGUN TO OPERATE UNDER ITS OWN POWER WITH SAID THROTTLE VALVE AT ITS CLOSED POSITION COMPRISING THROTTLE ACTUATED MOVEMENT LIMITING MEANS COOPERABLE WITH SAID THROTTLE VALVE TO MOVE THEREWITH INTO SAID PATH TO ABUT SAID CHOKE VALVE MOVEMENT LIMITING MEANS AND BLOCK AIR FLOW INDUCED OPENING OF SAID CHOKE VALVE BEYOND SAID STARTING POSITION UPON MOVEMENT OF SAID THROTTLE VALVE TO SAID IDLE POSITION AND TO MOVE OUT OF SAID PATH TO ENABLE OPENING OF SAID CHOKE VALVE UPON MOVEMENT OF SAID THROTTLE VALVE FROM ITS IDLE TO ITS OPEN POSITION. 